The present invention is directed to bicycles and, more particularly, to an apparatus for controlling a bicycle shift device based on movement of the bicycle shift device.
Bicycle transmissions that comprise front and rear derailleurs or internal hub transmissions are well known. In derailleur transmissions, the front derailleur shifts a chain among a plurality of front sprockets that are coaxially mounted to the pedal crank shaft, and the rear derailleur shifts the chain among a plurality of rear sprockets that are coaxially mounted to the rear wheel. Internal hub transmissions include a planetary gear mechanism disposed inside of a wheel hub and a clutch mechanism that switches the planetary gear mechanism to provide a plurality of power transmission paths. It is also known to use electric motors to operate the front and rear derailleurs or the internal hub transmission. Such a system is shown in Japanese Patent Application No. 2002-87371.
Electrically operated bicycle transmissions may operate manually or automatically. In manually operated electrical bicycle transmissions, a button or lever on a shift control device mounted to the bicycle handlebar is manipulated so that a gear shift command is output to operate the motor and upshift or downshift the bicycle transmission accordingly. In automatically operated electrical bicycle transmissions, gear shift commands are generated automatically based on bicycle speed.
In conventional electrically operated bicycle transmissions, when a gear shift command is received, the motor is operated continuously until gear shifting is completed. However, in derailleur-based transmissions, when a large amount of power is required to move the derailleur from one sprocket to another, such as when there is a problem with the chain, or when the gear shift operation is carried out when the bicycle is stationary, the motor may become overloaded and stop moving during the gear shift operation. Similarly, with internal hub transmissions, it may be difficult to operate the clutch mechanism during strong pedaling forces, and again the motor may become overloaded and stop moving during the gear shift operation. Because the derailleur or internal hub transmission has not arrived at the next gear position when the motor stops moving in such situations, electric power continues to be supplied to the motor. As a result, electric power may be wastefully supplied from the battery or other power supply, thereby shortening the life of the power supply.